The palladium-catalyzed addition of various vinyl compounds to dimethyl acetylenedicarboxylate

A New Route to Substituted Phenols by Cationic Rhodium(I)/BINAP Complex-Catalyzed Decarboxylative [2 + 2 + 2] Cycloaddition

“…Instead of alkynes, alkenes possessing a leaving group can be employed as alkyne equivalents. As such, Takeuchi and co-workers first reported a neutral iridium(I)/dppe complex-catalyzed [2 + 2 + 2] cycloaddition of a 1,6-diyne with n -butyl vinyl ether at elevated temperature (70 °C), which furnishes a tetrasubstituted benzene through elimination of n -butanol in moderate yield. − Following this pioneering report, our research group recently reported cationic rhodium(I)/BINAP complex-catalyzed [2 + 2 + 2] cycloadditions − of 1,6-diynes with enol ethers . The high Lewis acidity of the cationic rhodium(I)/BINAP complex facilitates the elimination of an alcohol even at room temperature, which significantly improved the yields of the desired tetra- and pentasubstituted benzenes.…”

Liquid Enol Ethers and Acetates as Gaseous Alkyne Equivalents in Rh-Catalyzed Chemo- and Regioselective Formal Cross-Alkyne Cyclotrimerization

“…Although gaseous alkynes such as acetylene and propyne can be used for the transition-metal-catalyzed alkyne cyclotrimerization, alternative liquid reagents are more convenient to handle than gaseous alkynes using conventional laboratory equipment. As such, commercially available and cheap liquid enol ethers and acetates are possible gaseous alkyne equivalents as shown in Scheme . , If a [2 + 2 + 2] cycloaddition of two alkyne units with one enol ether or acetate could proceed, initially formed cyclohexadiene A would be aromatized to the corresponding substituted benzene through elimination of alcohol or acetic acid. , Our research group already demonstrated that cationic rhodium(I)/BINAP-type bisphosphine complexes [BINAP = 2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl] are highly effective catalysts for [2 + 2 + 2] cycloadditions of alkynes with not only monoynes but also monoenes . In this paper, we describe a cationic rhodium(I)/rac-BINAP complex-catalyzed chemo- and regioselective formal cross-cyclotrimerization of alkynes with enol ethers or acetates.…”

Alkyne Surrogates in Cycloaddition Reactions for the Preparation of Molecules of Interest

“…To the best of our knowledge, such formal cross-alkyne cyclotrimerisation was firstly reported by Stephan and coworkers under palladium catalysis in 1993. [42] The reaction of a preformed palladium complex with dimethyl acetylenedicarboxylate and an excess of vinyl propionate or vinyl ether afforded selectively the corresponding aromatic compounds isolated alongside with propionic acid or alcohol, thus confirming a β-H elimination step from the cyclohexadiene intermediate. Since this original report, this strategy has been extended to other more efficient catalytic systems.…”